High-quality ZnS, ZnSe, and ZnTe epitaxial films were grown on ͑001͒-GaAs-substrates by molecular beam epitaxy. The 1s-exciton peak energy positions have been determined by absorption measurements from 2 K up to about room temperature. For ZnS and ZnSe additional high-temperature 1s-exciton energy data were obtained by reflectance measurements performed from 300 up to about 550 K. These complete E 1s (T) data sets are fitted using a recently developed analytical model. The high-temperature slopes of the individual E 1s (T) curves and the effective phonon temperatures of ZnS, ZnSe, and ZnTe are found to scale almost linearly with the corresponding zero-temperature energy gaps and the Debye temperatures, respectively. Various ad hoc formulas of Varshni type, which have been invoked in recent articles for numerical simulations of restricted E 1s (T) data sets for cubic ZnS, are discussed.

We have grown ZnSe layers by molecular beam epitaxy (MBE) on GaAs substrates which were deoxidized by atomic hydrogen at different temperatures. The surface roughness of the GaAs substrate was measured by atomic force microscopy (AFM); that of the growing ZnSe layers was determined from AFM measurement and the full width at half maximum of the reflection high-energy electron diffraction (RHEED) reflexes during the nucleation process and the layer growth. We find a strong influence of the substrate temperature during the deoxidization process on the surface roughness and the density of extended defects in the ZnSe layers. The density of extended defects was measured using high-resolution x-ray diffraction and spatially resolved cathodoluminescence (CL) images which were obtained at the defect-related Y 0 emission at about 474 nm. We find that the intensity ratio of the defect-related Y 0 emission and the near band edge excitonic emission is proportional to D 2.9 where D is the density of extended defects in the layer. We explain this relation by a model calculation which assumes radiative and non-radiative recombination of bound excitons as well as radiative recombination of electron-hole pairs via recombination centres which are involved in the Y 0 transition.

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We investigated the GaAs/ZnSe interface and the influence of the Ga 2 Se3 formation at the GaAs/ZnSe interface on the relaxation of the ZnSe epilayer using reflection high-energy electron diffraction, atomic force microscope, photoluminescence, and X-ray diffraction techniques. An improvement of the surface roughness due to the cleaning of the GaAs substrate with hydrogen excited in a plasma source and a higher critical thickness of GaAs(001)/ZnSe due to the suppression of Ga2 Se3 at the surface was observed.

ZnSe diodes grown on (100) GaAs substrates by molecular beam epitaxy were investigated using cathodoluminesence (CL) measurements at sample temperatures between 50 and 300 K. The CL line scans at different photon energies were performed on cleaved p–n junctions at 50 and 300 K, respectively. Taking into account surface recombination, carrier generation volume, carrier diffusion and internal built-in electric field and related carrier drift, the CL measurements from cleaved p–n junctions could be qualitatively explained. The charge depletion layer has a strong influence on the CL measurements. The calculated charge depletion width is in good agreement with CL measurements. The experimental data from the spatially resolved CL on the cleaved ZnSe diodes revealed important information of the carrier dynamics and recombination processes in these devices.